Automatic regulating means for grinding machines



March 12, 1957 ARTER 2,784,535

AUTOMATIC REGULATING MEANS FOR GRINDING MACHINES Filed July 29. 1952 s Sheets-Sheet 1 AUTOMATIC REGULATING MEANS FOR GRINDING MACHINES Filed. July 29, 1952 H. ARTER March 12, 1957 8 Sheets-Sheet 2 March 12, 1957 H. ARTER Filed July 29. 1952 I 3 Q 21 3 Q o g Q a: I m? I 8 Sheets-Sheet 3 r J I I I I I I I I I I I I l I I I I I I I I l I i I l I Daveaaibr March 12, 1957 H. ARTER 2,784 535 AUTOMATIC REIGULATING MEANS FOR GRINDING MACHINES Filed July 29, .1952 8 SheetsSheet 4 March 12, 1957 ARTER 2,784,535

AUTOMATIC REIGULATING MEANS FOR GRINDING MACHINES Filed July 29, 1952 8 Sheets-Sheet 5 H. ARTER March 12, 1957 AUT 8 Sheets Sheet Filed July 29, 1952 March 12,

H. ARTER AUTOMATIC REGULATING MEANS FOR GRINDING MACHINES Filed July 29. 1952 8 Sheets-Sheet 7 March 12, 1957 ARTER 2,784,535

AUTOMATIC REGULATING MEANS FOR GRINDING MACHINES Filed July 29. 1952 S Sheets-Sheet 8 300 ,sje I 3: i Mama 1 Invezziofl:

7 am fig ma United States Patent AUTOMATIC REGULATING MEANS FOR GRINDING MACHINES Application July 29, 1952, Serial No. 301,504

10 Claims. (Cl. 51-105) This invention relates to grinding machines of the class employed to grind bushings, pins, rolls, and various other articles having, for example, cylindrical or other types of exterior surfaces and, more particularly, the invention is concerned with speed control means for regulating the speed of rotation of work piece holders commonly used in grindingrnachines of this class.

Machines are now available for performing grinding operations automatically on work of this general character, and such machines include mechanism for presenting an article of work to a pair of work holders which grasp it and support it for the grinding operation and which later are operated to release the work piece. In these machines mechanism also is provided to move the grinding wheel toward and from the work and to perform other operations which are essential in accomplishing the objects for which these machines are designed.

It has been found, however, that difiiculty may occur in carrying out satisfactory grinding when dealing with eccentric or out of round parts which are required to be finished, and especially so where a high degree of accuracy in grinding may be exceedingly important. Trouble develops from the fact that a condition of eccentricity or out of roundness in a work piece to be ground may set up pressure variations between the grinding wheel and the work piece during each rotation of the latter member. Such pressure variations have a very definite tendency to spring the work piece and in some cases also the work holding mechanism, with the result that the work pieccas finally ground is still out of round or eccentric, although generally to a lesser extent than when received.

It is an object of the present invent-ion to deal with the problem indicated and in general to devise a method and apparatus for satisfactorily grinding eccentric or out of round work parts. Another object of the invention is to devise a work holder speed control which allows the work holders to operate at more than one speed during the grinding operation and which may be selectively controlled in response to changes in the position of the grinding wheel from time to time. Still another object is to provide a multispeed work holder control for use with a grinding machine having a special type of approach movement.

These and other objects and novel features will be more fully understood and appreciated from the following description of a preferred embodiment of the invention selected for purposes of illustration and shown in the accompanying drawings, in which t Fig. 1 is. a plan view of an automatic grinder organized in accordance with the present invention;

Fig. 2 is a front elevation of the machine shown in Fig. 1;

Fig. 3 is a right-hand end view of the machine;

Fig. 4 is a vertical, sectional view through one of the work holders and part of the operating means for it;

. Fig. 5 is a vertical, sectional view taken approximately Patented Mar. 12, 1957 through the axis of the grinding wheel but illustrating some parts in elevation;

Figs. 6 and 7 are vertical, sectional views taken approximately on the lines 6-6 and 7-7, respectively, of Fig. 5;

Fig. 8 is an elevation of the valve forming part of the hydraulic operating mechanism for producing the approaching movement of the wheel to the Work during the grinding operation;

Figs. 9 and 10 are sectional views taken on the lines 11--11 and 1212 of Fig. 10;

Fig. 11 is an elevational view further illustrating the switch and actuating arm control mechanism; and

Fig. 12 is a schematic wiring diagram further illustrating the speed control arrangement and parts of the direct current operating circuit;

Fig. 13 is a view somewhat similar to Fig. 12 but illustraining diagrammatically a hydraulically operated control; and

Fig. 14 is another view similar to Figs. 12 and 13 but illustrating an alternating current circuit control.

As noted above, it is customary in holding work pieces of the general class indicated, to employ two work holders which are adjustable toward and away from one another into positions such that they grip and solidly hold the two opposite extremities of a work piece. It is important that the work holders be rotated at synchronized speeds, and for ordinary cylindrical grinding operations it is understood to be the case that most efiicient grinding can be carried out by driving the work holders, for example at speeds from 300 to 500 R. P. M.

I have found that pressure variations and consequent deformation of eccentric or out of round work pieces, resulting from rotating these Work pieces at speeds of the magnitude indicated, may be substantially reduced or eliminated by employing a multispeed control for the work holders. With the aid of this multispeed control, initial or contact grinding may be carried out While the Work holders are turning at greatly reduced operating speeds and for a limited period, during which those portions of the work piece which comprise the eccentric surfaces are ground to approach a true cylinder. Thereafter the finish grinding may be completed at relatively higher, more conventional speeds.

Accordingly, I have devised a mechanism for providing a multispeed control of the work holders, and I further accomplish this control while providing for a continuously synchronized relationship of two indepnedent driving means for the respective holders. I have also devised a means for selectively changing the work holder rotative speed in response to change in position or move ment of the grinding wheel as it grinds away the parts of the work piece causing the eccentricity. In this way I accomplish a greatly superior and more .eflicient grinding result since the low speed grinding is only utilized for just the period necessary to remove the eccentric parts of the work piece, and thereafter the usual higher rotative speeds are allowed to take eiiect.

In one preferred embodiment the speed. control mechanism of the invention may be advantageously applied in a grinding machine of the type described and claimed in U. S. Pat. No. 2,517,193. The applicant in the present invention was a joint inventor, with one other, of the invention covered in this patent. The speed control mechanism of the present invention has, therefore, been illustrated in the drawings in association with parts of the machine described and claimed in said patent and particularly relating to an approach movement included therein.

Important parts of the speed control. of the present invention are two independently driven D. C. motors of the same general type as has been shown for driving the work holders shown in said Pat. No. 2,517,193. I have found that I may selectively control the speed of these motors in a desirable and novel manner by employing electronic means in conjunction with a multiple potentiometer arrangement. I have also found that I may advantageously combine electronic means, such as a Thymotrol control, with an approach movement for a grinding wheel, such as the approach movement shown in Pat. No. 2,517,193.

Accordingly, there will first be described parts of the grinding machine of said patent including its approach motion in sufficiently detailed particularity as to furnish a clear understanding of the operation involved and thereafter a description of the novel parts of the Thymotrol controlwill be given.

In the structure shown in the drawings, there has been illustratedin Figs. 1, 2 and 3 a grinding machine generally including a pair of Work holding chucks 2 and 2' and a grinding wheel 4 Whose operation is described in detail in Patent No. 2,517,193.

Work holding mechanism and operating means therefor For convenience, the work holders 2 and 2 above referred to, may be designated as the tail and head stocks, respectively, although they are alike in construction and are similarly operated. Fig. 4 shows the tail stock in considerable detail. It comprises a collet of a common form mounted in the end of a hollow spindle 5, this spindle being supported by anti-friction bearings 66 to revolve rapidly in a spindle body or sleeve 7. The body itself is supported for limited axial sliding movement in a stationary chuck cylinder or housing 8. At its rearward end portion the spindle is splined to thehub 10 of a pulley 11, this pulley being supported on ball bearings for rotation in the chuck cylinder 8. It is connected by a V-belt drive with the electric motor 12, Fig. 1, supported on the machine frame. Consequently, the entire chuck assembly can be revolved by power and the chuck can be moved axially while it is so revolved.

In order to move the chuck backward and forward to engage and release a work piece, such as that shown at W in Fig. 4, the chuck sleeve is supported to slide in the cylinder 18, as above mentioned, and an hydraulic mechanism'i's provided to reciprocate this sleeve and the parts mounted in it. This mechanism comprises a cylinder 13, Fig. 4, mounted on top of the casing 8, with a double piston '14 working in it, this piston having a tongue or lug 15 extending downwardly from it through slots in the cylinders 8 and 13, with its lower end entered in a socket formed in the upper side of the sleeve 7. Consequently, when fluid is supplied to one end or the other of the cylinder 13, by a suitable valve mechanism, the sleeve 7, with its spindle and the chuck 2, will be moved backward ,orforward in accordance with the direction of pressure applied by the fluid.

Turret structure and operating mechanism therefor A turret mechanism corresponding to that of U. S. Pat. No. 2,517,193 is indicated in Figs. 1 and 3. It com- PIiSCS'B. body of cylindrical fonn having a series of nearly circular pockets formed in its peripheral section and of such dimensions with reference to the work pieces that these pieces are somewhat loosely received in them with a Part of the edge of each work piece projecting for an appreciable distance beyond the periphery of the turret. Because the work pieces are initially presented to the chucks 2 and 2 by the turret, it is important that the turret shall be so constructed and its operating mechanism shall be designed in such a manner as to present the work accurately to the work holders so that they can pick it up and center it automatically as they move toward each other to engage and clamp the work. Reference may be had to said U. S. Pat. No. 2,517,193 for an understanding of further details of construction of the turret mechanism. It will be understood that the work pieces are fed into the turret by hand as the pockets come around to the upper part of their path of rotation and are ejected by an ejector rod mechanism which is also described in detail in said Pat. No. 2,517,193 just referred to.

Grinding wheel head and approach motion Referring to Fig. 5 it will be seen that the grinding wheel 4 is keyed to the left-hand end of a shaft 48 supported in suitable hearings in a wheel head 50 which is in U. S. Pat. No. 2,535,997, dated December 26, 1950,

and reference may be had to this patent for an understanding of the details of this mechanism. Briefly, it involves an electric motor controlledby switches mounted on a control panel and operable to move the entire wheel head assembly either at a high speed or a low speed, as

desired, toward or from the work, and the degree of movement can be easily read on large dials contained in the casing 52, Figs. 2 and 3.

In accordance with the invention I provide, for use with the above described machine, an electronic-type control apparatus which is operatively connected to the sleeve or quill 55 above described. Attention is directed to Figs. 3 and 5 in which is shown an arm 200 operatively connected to an outer exposed end portion of the quill 55 and positioned such that it is adapted to swing with this member when the latter is rotated. Fixed at a nearby convenient point on a stationary part of the grinding machine is a switch member 201 having an actuating pivot element 202 adapted to be set in the path of movement of threaded stop 204 carried at the upper end of the arm 200, as is better shown in Fig. 3. The setting for the actuating pivot element 202 is made with reference to register of arm 200 with a scale 206 also fixed to a stationary part of the grinding machine in a position such as that shown in Fig. 3, and the scale divisions of the scale 206 are chosen with refreence to the distance through which the quill member moves in making its approach and return motion to adjust the grinding wheel,

as described above. By means of this scale a series of positions may be made available which will include a series of approach positions for different sized diameter work pieces assumed by the grinding wheel in reaching a point in which eccentricity of the work may be largely removed.

The switch member 201 when contacted by the stop 204' operates a control circuit which includes a variable speed Thyratron tube drive, Fig. 12. This drive, in turn, controls the speed of work holder rotation through the two electrical D. C. motors l2 and 12', as shown in Fig. 12.

As a feature of'the invention I provide in this circuit two potentiometers P1 and P2 and I take the leads from these potentiometers and connect them through two switches of a two-pole double throw relay G. The switch to which P1 is connected is normally closed while the switch to which P2 is conected is normally open as shown in Fig. 12. These potentiometers may be set at desired positions by means of control buttons 210 and 212 located on the control panel, as shown in Fig. 3.

One of these potentiometers controls high speed motor operation and the other controls low speed motor operation. Thus the circuit normally operates with a potentiometer setting of potentiometer P1 such that a circuit is closed through the Thymotrol to actuate the motors 12 and 12 at a desired relatively low operating speed. At some desired point in the grinding operation, determined by the setting of the arm 200, the switch 201 will be automatically closed, which closes the circuit through the relay G and also closes'the circuit through the potentiometer P2. The Thymotrol control then acts to increase the speed of the motors 12 and12' to a desired higher operating speed.

An important feature of the invention, therefore, is the combination with a Thymotrol control of two separate Potentiometers which are, nevertheless, independently adjustable so that one controls the high speed operation of the motor'and the other controls the low speed operation of the motor, yet each potentiometer is of an equal rating. This allows the potentiometers to be adjusted to a common setting and, as a result, the normal high speed grinding motor may operate directly on a work piece having no eccentricity.

By setting the low speed potentiometer, one can initiate multispeed grinding at will to take care of occasional or frequently occurring out of round work pieces. In actual practice it is found that very excellent results are obtained with articles such as eccentric pins and bushings, for example, by setting of the low speed potentiometer in a control position to cause the work holders to revolve at speeds of 40 to 50 R. P. M. At such speeds it is definitely found to be the case that grinding can take place without springing of the work or the work holders, and a correction of eccentricity can be effectively made. This takes place during the operation of the approach movement earlier described in the specification and the correction can be related to the setting of the control arm 200, so that at the point at which the approach movement reaches a predetermined point, the high speed potentiometer takes over control in response to tripping the arm 200. Grinding then proceeds at speeds of as high as 500 R. P. M. to the extent required for a true grinding being obtained.

It will be observed that the preferred form of the invention described makes use of a D. C. source of current owing to the desirable flexibility characteristics and simplicity of construction inherent in this type of control mechanism. However, I may desire to modify this form of the invention in one or more respects, for example, in the manner illustrated in the two additional embodiments of the invention shown in the drawings in Figs. 13 and 14.

Thus, in Fig. 13 work holders 300 and 302 of the same construction as earlier described, may be connected in driving relationship with two independent hydraulic motors 306 and 308; and this apparatus is noted diagrammatically as being connected by means of the usual fluid conduits 310 and 312 to a valve 314 which controls flow of fluid as it is forced by a pump 316 and electrical motor .318 out of a tank 320. A linkage 322 may be connected :to a moving part of the valve 314, and in response to ;movement of the arm 200' secured to a wheel quill 55, .may gradually open the valve 314 and thus increase the :speed of the hydraulic motors 306 and 308.

Another suitable arrangement is to employ independent A. C. motors, as shown in Fig. 14, wherein 'work holders 330 and 332 are connected in driving relationship with two A. C. motons 334 and 336. These motors are equipped with conventional variable pitch :sheaves of well known construction and which can be varied in position to change the speed of the spindles. These sheaves are acted upon by a pair of air cylinders i338 and 340, in turn connected to a valve 342 which con- 'trols flow of air in to and out of inlet pipe 344 and outlet pipe 346. The valve 342 is of the relay controlled type, and when energized by closing of the switch 348 through movement of an actuated arm similar to arm 200 above .noted may control operation of the A. C. motors in a .selective manner.

It will be evident from the foregoing description that I have provided a novel and efiicient means of controlling two independently driven work holders in such a manner that I may, in dealing with eccentric work pieces, grind initially at relatively low operating speeds which will :avoid springing or distorting the work, or the work pieces, and yet I may, at will, increase the grinding speed at a point dictated by removal of eccentricity to complete grinding at high operating speeds. There is thus achieved a very substantial and desirable saving in time and labor with a marked increase in accuracyof the ground sur- Having thus described my invention, what I desire to claim as new is:

1. In a machine for grinding rotary pieces of work, a pair of opposed holders for supporting and revolving a work piece around its own axis, a pair of independent electric motors of the direct current type, a grinding wheel, means for supporting the work holders in axial alignment with each other to grip the opposite ends of a piece ofwork and revolve it around said axis while said wheel acts on the work piece, said electric motors being connected with the work holders to drive them, and a common speed control mechanism operatively connected to said independent electric motors to provide for synchronized speed changes in the said motors.

2. In a machine for grinding rotary pieces of work, the combination of a grinding wheel, head and tail stocks, means for supporting them in axial alignment with each other to grip the opposite ends of a piece of work and revolve it around said axis while said wheel acts on the peripheral surface of the work piece, independent electric motors connected with the respective head and tail stocks to drive them, said motors being of the direct current type, and a common current supplying means for the electric motors, said common current supplying means being responsive to movement of the grinding wheel to provide for synchronized speed changes in the said motors.

3. A device as described in claim 2, in which the current supplying means includes a gas triode tube type, potentiometer means for regulating the voltage output from the triode tube to the motors, relay means for selectively connecting the potentiometer means with the gas triode tube, a switch for energizing the said relay, and mechanism operative to actuate the said switch.

4. A structure according to claim 3, in which the mechanism operative to actuate the swtch is operatively connected to the grinding wheel.

5. A structure as defined in claim 4, including means for producing an approach motion of the said grinding wheel toward the work, and means responsive to movement of the approach means for actuating the said switch.

6. In a machine for grinding rotary pieces of work, a pair of work holding chucks for supporting and revolving a work piece around its own axis, independent motor means for driving said work holder means, a grinding wheel, a wheel head in which said wheel is mounted for operation on the work piece so supported and revolved, means for revolving said wheel rapidly around its own axis, the mounting for said wheel comprising a spindle, an eccentric quill supporting the wheel spindle for oscillating movement about an axis parallel to the axis of said spindle, means for oscillating said quill about its axis, and a common speed control mechanism for the said independent motors, said control mechanism including means for producing synchronized speed changes in said motors.

7. A structure as defined in claim 6, in which the speed control means includes a source of direct current, means for regulating the voltage output of the direct source, an electrical device for selectively connecting the said regulating means with the speed control means, a switch for energizing the said electrical device, and mechanism responsive to movement of the said quill .for actuating the said switch.

8. A structure as defined in claim 7, in which the said mechanism responsive to the quill comprises an arm attached to the quill and adapted to be rotated with it during Refererices'Cit ed, in the file of this patent UNITED STATES PATENTS 1,909,155 Webs'ter' May 16; 1933 8 Dall-- 'Mar.- 27, 193.4; cn

A 4 19 Maurer' 1 May 11,- 1937 Benedek 1.1. -1-- Nov. 9, 1937 Silven' e e Apr. 5, 19-38 Herman Mar. 7, 1939 Flygare Apr. 22, 1941 Rutemiller Nov. 29, 1949 Fraser Aug. 1, 1950 Belden July 3, 1951 FOREIGN PATENTS Germany May 31, 1932 Great Britain Jan. 24, 1951 

